Hungarian Veterinary Archive

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Title:

Role of insulin in the development of metabolic and reproductive malfunctions of periparturient dairy cows

Author:

Kerestes, Ágnes Mónika

Date:

2009

Abstract:

In dairy cows selected for high milk production theperiparturient insulin resistance
(IR) may play a pivotal role both in adaptation to the energy demands of milk synthesis
and in the pathogenesis of some metabolic malfunctions and organic diseases related to
the negative energy balance (NEB). Insulin is the most important anabolic hormone with
significant functions in carbohydrate, lipid and protein metabolism, which acts to
maintain body depots and to prevent ketogenesis. Moreover, insulin is one of the key
metabolic molecules which mediate the crosstalk between the hypothalamic-ovarian axis
and the body energy state. In humans the release ofcytokines, that occurs in association
with obesity and inflammatory diseases (especially in those with endotoxemia), and the
release of non esterified fatty acids plays an important role in the development of IR. In
dairy cow inflammatory diseases with intensive endotoxin/cytokine release (puerperal
mastitis and metritis, clinical endometritis) are frequent complications in the puerperal
phase. Our understanding on the relationship between periparturient metabolic disorders,
insulin resistance and the poor reproductive performance in the modern dairy cow is
limited, yet.
Our goal was to investigate the periparturient insulin pattern and IR in high lactating
dairy cows in relation with some metabolic and reproductive malfunctions and to improve
postpartum ovarian function through energy supplementations in cows under different
management systems.
We showed that pancreatic ß-cell function and the biological potency of insulin is
impaired in cows with long-term hyperketonemia. Short-term elevations in plasma free
fatty acids and ketone bodies may not potentially induce further increase in peripheral
tissue insulin resistance in the early lactation. However, severe inflammatory diseases like
puerperal metritis may potentially further depress insulin secretion of the pancreatic ß-cells and the whole body insulin responsiveness of dairy cows, with long-term effects on
metabolism and reproduction. Furthermore we also found that the revised quantitative
insulin sensitivity check index (RQUICKI) as was assessed earlier only in healthy
animals should be applied with cautions in the assessment of insulin sensitivity in dairy
cows in different physiological and disease states (Exp. 1). We found that top-dressing of
pulverized propylene glycol (PGL) on the total mixed ration from d 14 before calving till
d 10 after calving was not effective in improving metabolic profile, insulin sensitivity, the
time of first postpartum ovulation and pregnancy rate. Most probably the relatively good
energy balance of the animals involved in our studylimited the effectiveness of the
supplement. However, the method of allocation and the absorbent incorporated for the
PGL product used in the present study contributed to the inefficacy (Exp. 2). In contrast,
in lean cows, which were kept under pasture condition, the pre-partum supplementation
with cracked corn grain improved the energy balance, peripheral insulin concentrations
and decreased the time to the first pp ovulation. (Exp. 3).It is obvious that the
effectiveness of periparturient energy supplementation is greatly dependent on the initial
energy state of the animals.
We hope that our results contribute to our understanding on dairy cow physiology and
help to choose appropriate dietary tools in improving metabolic and reproductive
performance.